US2407857A

US2407857A - X-ray tube

Info

Publication number: US2407857A
Application number: US472068A
Authority: US
Inventors: Verhoeff Adrianus
Original assignee: Hartford National Bank and Trust Co
Current assignee: Hartford National Bank and Trust Co
Priority date: 1941-02-27
Filing date: 1943-01-11
Publication date: 1946-09-17
Anticipated expiration: 1963-09-17
Also published as: NL59156C; GB553084A; BE444657A; FR879753A; CH239102A

Description

Sept- 17, 1946- A. vERHoEl-F I X- RAY TUB E Filed Jan. 11,; 194s i 16, I il' y@ x zizi/l sa :5154 2:46 a; iffA me/whoa,

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Aranu Patented Sept. 17, 1946 2,407,857 X-RAY TUBE Adrianus Verhoeff, Eindhoven, Netherlands, assignor to Hartford National Bank & Trust Company, Hartford, Conn., trustee Application January 11, 1943, Serial No. 472,068 In the Netherlands February 27, 1941 (Cl. Z50-143) 10 Claims. 1

X-ray tubes having a comparatively great mean load require measures for cooling the anode. Various means may be used to withdraw heat from the anode. In tubes for diagnostic work the operating temperature of the anode must remain far below the maximum admissible anode temperature to prevent heat shock. The usual expedient is to fix a heat conductor to the anode, for example conductor shaped in the form of a metal rod which extends through the wall of the tube behind the anode and has a radiating surface outside the tube.

With tubes comprising a safety jacket the presence of such a heat radiating member having the potential of the anode is inconvenient for several reasons and it has therefore previously been suggested that the heat transfer should be effected by radiation from the anode towards that part of the tube wall which surrounds the anode instead of being effected by transmission. By this wall which is generally maintained at earth potential,

the heat can be readily transmitted to the surrounding air or to a cooling medium.

Although this means of cooling the anode yielded satisfactory results thanks to a combinaference of not more than 300 C. away from the vanode to the space outside the vacuum of the tube. The term wholly or in part is to be understood to mean here that in a radial direction, and hence not in an axial direction, the body may consist wholly of insulating material or may consist of alternating laminae of conducting and insulating materials.

It is essential that the insulating material be capable of withstanding the full tension existing between the anode and earth, said tension being about half the operating voltage of the tube.`

It is dimcult to manufacture and place in position an insulator that fits so accurately around the anode that a satisfactory heat conducting,

contact may be set up between the wall of the p anode and that of the insulator. According to .the invention, this difficulty can be obviated by a resilient member of goodheat conductivity which engages the walls of the intermediate space with slight pressure and transmits the heat from one wall to the other. This affords good heat conduction and enables free expansion and con, traction due to temperature changes. This resilient member may be constituted for example by a cylinder of corrugated sheet metal.

The principle of the invention may be carried -into practice in various ways, The insulator may y form part of the outer Wall of the tube :and thus serve to absorb both the electric voltage and the air pressure.

As an alternative, the insulator may be wholly arranged within the vacuum of the tube., In this case, the heat has therefore still to `be conducted from the insulator to that part of the outer wall of the tube by which it is surrounded and which in this case may be of metal. In order to assist good heat transmission between the insulator and the tube wall, it is preferable that a resilient member, for example a metal sleeve of corrugated sheet metal should be arranged in the manner mentioned before for the conveyance of the heat from the anode to the insulator.

The insulator may be made of ceramic material, for example china. This material is capable of withstanding heat, may be readily freed from gases and is Vgenerally a suilicient heat conductor and electrical insulator.

In the construction according to the invention the heat is conducted away by a body which is required to be a good electrical insulator. Although as a rule the heat conductivity of electrical insulators is much less than that of metals, sufficient heat can be conducted away in this case by the insulator due to the fact that the direction in which the energy ows off is normal to the surface and this latter may be made comparatively large so that but little heat per unit of section needs to be conducted away. Moreover, the heat has only to traverse a comparatively short path. The conditionsare consequently just the reverse as compared with tubes having a cooler at the end, because in the latter case the section of the (metal) heat. conductor is much smaller and its length is much greater as compared with the tube according to the invention.

In order to increase the surface over which theV heat dissipation is distributed the anode as a whole need not be made particularly long but it is suflicient to shape it into the form of a hollow tube, for example a cylindrical tube, which dissipates the heat and transmits it to the surrounding body and which comprises a bottom or intermediate wall carrying the anode mirror.

The circumstance that the anode is in heatconducting contact with a body7 surrounding it may be taken advantage of to cause it to be so supported by this body that that part of the wall which seals the tube at the end behind the anode is not given any mechanical load by the anode weight. This latter part which thus only serves for insulation and for sealing the vacuum'must give passage to the current supply lead of the anode which may therefore be very thin so that heat is not conducted away along this path. The tube end which can be closed by a cable end piece thus remains cool due to the fact that a direct heat-conducting connection to the anode is missmg.

.For sealing the tube at the ends use may also be made of disc-shaped glass-like members comprising finely divided cavities (so-called sponge glass) which permits metals and insulating materials having widely diierent coeicients of expansion to be sealed together to thereby obtain a vacuum-tight seal.

In order that the invention maybe clearly understood and readily carried into eiect it will now be set out more fully with reference to the accompanying drawing in which two forms of construction of X-ray tubes according to the invention are shown in section. By means thereof some details obtained by further development of' the invention will be mentioned.

' Fig. l is a longitudinal sectional view of an X- ray tube having a heat-conducting insulating body arranged entirely within the tube.

Fig, 2 is a cross-sectional View of the same tube taken on the plane I-I.

Fig. 3 shows a tube in which the heat conducting insulating body constitutes the outer wall of the tube.

Referring to the drawing, 1 designates an exhausted cylindrical metal vessel closed at the ends by glass sealing pieces 2 and 3. A cylindrical body of electrically insulating material, for example china or other ceramic material is gripped in the metal vessel b-y means of a resilient sleeve 4 of corrugated sheet metal of good heat conductivity',A for example copper.

The anode of the X-ray tube is gripped within the body 5 by a likewise resilient sleeve B of corrugated plate-shaped material. The anode comprises a cylindrical part 'lv and a block 8 both of metal kof good heat conductivity, for example copper. The cylinder 1 may be shrunk round the block 3 so as to afford good heat conduction.

The anode has secured to it a supply conductor 9 which is passed through the sealing piece 2 by means of a small metal disc li) sealed to the glass. The cathode Il is secured to the sealing piece 3 and has a normal construction,` details such as the leading-in wires sealed in the pinch and the filament being therefore omitted in the drawing. When the tube is in use the electrons are propelled by the electric neld between the two electrodes at such a speed against the anode mirror I2 that X rays are generated in situ. Essentially,

l however, the energy of the electrons is converted into heat and secondary electrons are also dislodged.

The X rays are absorbed for the greater part by the wall of the tube and other parts (all of which are not shown) which jointly surround the anode and in part may be provided deliberately for this purpose. A narrow beam of rays is transmitted. For this purpose the cylindrical part 1 of the anode 8 has an aperture i3 formed of the cathode.

in it, the body 5 is locally thinned at I4, the

sleeves

4 and 5 have a corresponding aperture formed in them and the metal wall I comprises a window closed by a thin small glass plate l5.

The heat is rapidly dispersed about the block t and thence it is transmitted to the cylinder l. The latter gives theanode a large surface of contact with the resilient sleeve 6 which in turn is in contact over a large surface with the china part 5.

Although the heat transmitted through each unit section of the part 5 is less than if it were made of metal the large extensiveness of the section which contributes towards the conveyance of heat and the short distance through which the heat has to be conveyed enable the heat to escape rapidly.

It is true that the spaces between the anode and the china part 5 and those between the latter and the tube wallare only filled in part 'but the gripping sleeves and 5. may be made of a metal having a much higher specific conductivity than the insulator 5.

The outside of the wallfi may, if necessary, be cooled artiliciallyv by a circulating gaseous or liquid cooling medium or by the provision of cooling ribs.

The withdrawal of heat from the wall l to the glass sealing pieces is avoided by the presence of Y thinned` edges l5. In addition, radiation of heat from the anode to the sealing piece 2- is prevented bythe bottom Il of the insulator 5'. The current lead 9 is so thin and klong that no appreciable heat'transmission occurs alongr it. The glass sealing piece 2 and the cable end-piece to be arranged thereon are thus safe-guardedV against heating.

' With X-ray'tubes of they construction hitherto in use the anode is supported by the re-entrant glass edge ofthe tube wall.

The invention permitsa sturdier construction to be obtained. It enables the anode to be carried solely by therside wall of the tube by uniting the resilient sleeves 4 and' and the insulator 5 with the anode and the metal wall l to form an Aunshakable unit, forY example by gripping, as

shown. The glass part 2 of the wall which seals the tube at the end' behind the anode is thus not given any mechanical load by the weight of the anode and thus the risk of breakage which is always impending in other tubes is averted.

The metal cylindricalV body l is also used for a further purpose. It is lengthened towards the side This arrangement has the Vadvantage that the part extending to the other side can be shorter and the heat is more readily' distributed about the entire length of the cylinder because it can flow from the centre to both sides moreover, the tube acts as a screen against secondary electrons. In order that this function may be most effective the cylindrical body is provided with a bottom i8 which has, of course, formed in it an aperture for the passage of the beam of cathode-rays. In addition, this aperture has an upright edge i9 turned towards the anode mirror in order also to retain electrons moving in a direction at a large angle with the axis of the tube, such as tertiary electrons proceeding from the inner wall of the cylinder l.

In so far as charged particles may still emerge `from the discharge space they are retained by the is formed by a block 2| and a cylinder 22, the block 2| carrying the anode mirror 23.

Again, the cylinder 22' is mounted an insulator 25 by means of a resilient sleeve 24 of corrugated sheet metal.

The insulator 25 constitutes the envelope of the tube, and

glass sealing pieces

26 and 21 are sealed to theedges of the insulator at 28 and 29. The insulator may be of china or of similar ceramic material to which glass can be fused. The anode is supported by the insulator 25 only and the sealing piece 2E solely serves for vacuum sealing the envelope and for the leading-through of the supply conductor 3D to the anode. For the purpose of increased safety the insulator may be coated on the outside with a layer of conductive mate rial (not shown). a

Similarly, the sealing piece 21 serves solely for sealing the vacuum and for leading-through of the supply leads 3l and 32 to the cathode. The latter are secured to studs which are arranged in a metal plate 35 from which they are insulated by glass beads 33 and 34 t0 the edge of which the glass Sealing piece 21 is sealed.

The cathode shell 36 is supported within the insulator 25 in a manner similar to the anode by means of a disc 31 having a bent-over edge 38 which is rendered resilient by the provision of a plurality of slits 39.

The heat produced in the anode in the use of the tube passes to the cylinder 22 and hence is led by the resilient sleeve 24 through a large sectional surface of the insulator 25 towards the outer surface of the tube, where it is dissipated by radiation or carried away by other means.

What I claim is:

1. An X-ray tube comprising an evacuated tubular envelope, an anode member having a heat-generating portion and being arranged within said envelope with its peripheral surface adjacent to and spaced from the inner surface of the envelope, and means to directly connect the said adjacent surfaces in heat conducting relationship comprising a memberof good heat con-Y ductivity whereby to transfer the heat generated at said portion to said envelope in a radial direction from the anode member and substantially entirely by conduction.

2. An X-ray tube comprising an evacuated tubular envelope, an anode member having a heatgenerating portion and being arranged within said envelope with its peripheral surface adjacent to the inner surface of the envelope, and means to directly connect the said adjacent sur-4 faces in heat conducting relationship comprising a resilient member of good heat conductivity, the heat generated at said portion being transferred to said envelope in a radial direction from the anode member and substantially entirely by con- V duction through said resilient member.

3. An X-ray tube comprising an evacuated tuto the inner surface of the envelope, and means to directly connect the said adjacent surfaces in heat conducting relationship co-mprising an electrical insulating member and a resilient member.;V

of good heat-conductivity surrounding said anode member and interposed between the said adjacent surfaces, the heat generated at said portion being transferred tosaid envelope in a radial direction from the anode member and substantially entirely by conduction through said insulating and'resilient members.

5. An X-ray tube comprising an evacuated tubular envelope, a hollow cylindrical anode member having a wall portion provided with an anode mirror and being arranged with its peripheral surface adjacent to the inner surface of the envelope, and means to directly connect the said adjacent surfaces in heat conducting relationship comprising an electrically insulating ceramic sleeve member and a cylindrical corrugated sheet-metal member 'surrounding the cylindrcal anode member and interposed between the said adjacent surfaces, the heat generated at the anode mirror being transferred to `said envelope a in a radial direction from said anode member and substantially entirely by conduction through said insulating and sheet-metal member.

6. An X-ray tube comprising an evacuated envelope, and a cathode member, an anode member spaced apart and enclosed within said envelope, said anode member comprising an anode mirror, a hollow cylindrical element enclosing the anode mirror, and means to collect secondary electrons from the anode mirror comprising a portion of the cylindrical element extending beyond the said mirror towards the cathode member, said cylindrical element being arranged within the envelope with its peripheral surface adjacent to the inner surface of the envelope, and

means to directly connect the said adjacent surfaces in heat conducting relationship comprising a member of goed heat conductivity whereby to transfer the heat generatedV at the anode mirror to said envelope in a radial direction `from said cylindrical element and substantially entirely by conduction.

1. A'n X-ray tube comprisingy an evacuated cylindrical metal envelope, an anode member within said envelope comprising a cylindrical metal sleeve arranged within the envelope with its peripheral surface adjacent to the inner surface of the envelope, an anode mirror within said sleeve and secured to the inner wall thereof, said anode sleeve having a portion which extends beyond the anode mirrorand is provided with an aperture in the wall thereof adjacent to the anode mirror and which comprises a flange portion having its edge inwardly facing the anode mirror, and means to directly connect the said adjacent surfaces in heat conducting relationship, said means comprising a cylindrical electrical insulating ceramic member surrounding the anode member 'and extending beyond the said flange portion thereof, a cylindrical corrugated sheet metal member interposed between and contacting the adjacently positioned surfaces of the ceramic and anode members and a cylindrical corrugated sheet metal member interposed between and contacting the adjacentlyl positioned surfaces of the ceramic member and the envelope, the heat generated at the said anode mirror `being transferred to the envelopein a.

radial direction from the anode member and substantially entirely by conduction through said cylindrical corrugated members and said ceramic member.

8. An X-ray tube comprising an evacuated tubular envelope, an anode member having aheat `generating portion and being yarranged within yyaid envelope with its peripheral surface adjacent to and spaced from the inner surface of the envelope, said anode member being supported within said envelope substantially entirely by the surrounding portion of the envelope, and means to directly connect the said adjacent surfaces in heat conducting relationship comprising a member of good heat conductivity whereby to vtransfer the heat generated at the said portion of the anode member to the envelope in a radialdirection from the anode member and substantially entirely by conduction.

9. An X-ray tube comprising an evacuated tubular envelope, a sealing member closing one end of the envelope, an anode member having a heat generating portion and being arranged within the envelope with its peripheral surface adjacent to the inner surface of the envelope, a voltage supply conductora for the anode member heat conduction from the anode member to said sealing member. Y

10. An X-ray tube comprising an evacuated tubular envelope', an anode member having a heat-generating portion and being arranged within said envelope with its peripheral surface adjacent to and spaced from and electrically insulated from .the inner surface of the envelope, and means to directly connect the said adjacent surfaces in heat conducting relationship co-m- Y prisingv a member of good heat conductivity whereby to transfer the heat generated at said portion to said envelope in. a radial direction from the anode member and substantially entirely by ccnduction.

Y v ADRIANUS VERHOEFF.